This is just a UK issue - and you can buy two packs of "any product containing paracetamol" usually. Some stores have a 32 rule and will only let you buy one pack if it has 32 in it. However, since you can simply go to the next store and buy more it is a ludicrous rule.

In the US you can walk into any store and buy the bulk bottles of 500 Tylenol (Paracetamol). I have never seen a statistic showing it increased the number of OD's so it is more of a safety from accidental over ingestion than deliberate I believe.